The Alaska Vegetation Classification - Alaska Geobotany Center ...

Glossary'Abundanc+(l) The total number of individuals of a species in an area, population,or community; (2) total number of individuals in a sample divided by the number ofoccupied sampling units gives relative abundance; (3) also may be expressedsubjectively on a five-part scale as very rare, rare, infrequent, abundant, and veryabundant.Active layer-The layer of soil above the permafrost that thaws and freezes annually.Age dlstrlbutlon-The classification of individuals of a population according to ageclasses or periods, such as prereproductive, reproductive, and postreproductive, orinto numerical intervals such as 10-year age classesAll-agebApplied to a stand of trees in which trees of all ages are found.AlluvlaCRefers to material transported and deposited by running water.Alluvial soil-Soil that has developed from transported and relatively recently depositedmaterial (alluvium), characterized by little or no modification of the originalmaterial by soil-forming processes.Alluvium-A general term for all detrital material deposited or in transit by streams,including gravel, sand, silt, clay, and all variations and mixtures of these.Alpine(1) Refers to those portions ot mountain landscapes above tree growth, orthe organisms living there; (2) that vegetation occurring between the upper limit oftrees (tree line) and the lower limit of snow (snowline) on mountains high enough topossess both of these features; (3) implies high elevation, particularly above tree line,and a cold climate.Alpine meadow-(1) A dense, low, meadowlike type of herbaceous plant coverfound above tree line: (2) low herbaceous vegetation dominated by grasses, sedges,and other herbs in the alpine zone; (3) nearly synonymous with alpine grassland.Alpine tundra-That portion of the landscape above the upper limit of tree growththat supports a plant cover of dwart shrubs and herbs.Annual plant-A plant completing its life cycle and dying in 1 year or less; forexample, Bromus tectorum.Aquatic plant, emerged or emersed-A plant adapted to life with its lower partssubmerged in water, its upper parts raised out of water.Aquatic plant, Immersed-A plant adapted for life submerged or almost submergedin water: for example, Myriophy//um spp.Aquatlc sltecSites permanently or at least characteristically flooded where alldominant plants are aquatics with floating or submerged leaves; for example, speciesof Potamogeton, Hippuris, Myriophy//um, and several others. Depth of water is notsignificant but its persistence is.Arctic-High-latitude region where tree growth usually is absent because of unfavorableenvironmental conditions (low temperatures, short growing season) andmore or less following the 10 OC mean daily isotherm for the warmest month of theyear. In general, north of 670 N. latitude; sometimes defined in Alaska as north of the"P-Y-K Line," or north of the Porcupine, Yukon, and Kuskokwim Rivers.' Definitions for terms are from Gabriel and Talbot (1984).254